https://www.martin-riedl.de/2018/08/24/using-ffmpeg-as-a-hls-streaming-server-part-1/



https://www.raspberrypi.org/forums/viewtopic.php?t=256572



https://github.com/arut/nginx-rtmp-module/wiki/Directives#record
https://www.wowza.com/blog/using-webrtc-as-rtmp-alternative
https://stackoverflow.com/questions/31451716/how-to-check-rtmp-live-stream-is-on-or-off